Electro-acoustic musical instrument



J. MAGER Oct. 27, 1931.

I ELECTED- COUSTIC MUSICAL INSTRUMENT Filed March 21, 1928 2 Sheets-Sheet 1 Oct. 27, 1931. J. MAGER 1,829,099

ELECTROACOUSTIC MUSICAL INSTRUMENT Filed March 21, 1928 2 Sheets-Sheet 2 I71 V617 for. fd'ry Mayer f M Patented Oct. 27, 1931 UNITED STATES J'dBG MAGER, OF BERLIN-NEUKOLLN, GERMANY ELECTED-ACOUSTIC MUSICAL INSTRUMENT Application filed March, 21, 1928, Serial No My invention relates to musical instruments and more particularly to instruments in which musical sounds are generated by means of one or more voice-frequency electron-tube generators. In such instruments a normal lowfrequency oscillatory circuit isprovided the elements of which, self-induction and capacity, are varied in order to vary the pitch of the circuit.

It is an object of my invention to provide an improved instrument of this type and to this end I arrange two high-frequency electron-tube generators the difference of frequencies of which is within the desired frequency range.

Instead of electron-tube generators, oscillations may be generated by gaseous conduction lamps or crystals.

By superposing the two high-frequency vibratio'ns, by rectification and, if desired, by amplification, the sound which corresponds to the difference of frequencies can be rendered audible'by means of a loudspeaker, and utilized for musical purposes.

By high-frequency oscillations those oscillations are understood which are beyond the limit of audibility. Preferably a highfrequency electron-tube generator and an oscillation audion are provided for generating the high-frequencies.

The electrical size of the two high-frequency circuits can be determined so that the total range of tones which are required for musical purposes is covered by rotation of a suitable rotating plate condenser, having, for instance, kidney-shaped plates. The advantage of this arrangement is that the perform ing of glissando-like passages between two sounds and a finer subdivision of the normal half-tone system into, for instance third, sixth, quarter and eighth tones, is facilitated.

A' musical instrument of the kind described may be designed with a keyboard the condenser for each sound being cut into an oscillation circuit by means of a key, and in such an instrument a finer subdivision of the halftone system may also be effected.

The intensity of the sound may be-varied by cutting in resistances, and the timbre of the-sound may be varied by suitably selected 263,450, and in Germany October 29, 1925.

- audion tubes and loud speakers. Polyphone play is efiected by combining one or more instruments.

The plate condenser may be operated by a lever on its shaft, an indicator on the lever 65 moving over a circular scale on which the several tones are marked so that every tone is readily found.

It has been discovered that during longer periods'of operation it will not be necessary to modify the scale as detuning of the apparatus does not occur. On the other hand, it may happen that the total range of tones becomes shifted and it is another object of my invention to provide means for balancing this. To this end, I vary the ultra-audible osc'llations by means of a rotating plate condenser until the original pitch of the beatnote has been reestablished.

At a suitable point, and preferably on the crank, a key is provided which controls the oscillation circuit and consequently the tone. The size of the condenser and the shape of its plates are so determined as to obtain the desired range and distance of octaves. Kidhey-shaped plates are preferred, as all octaves have an almost uniform pitch for equal distances. of tones which is particularly suitable for musical purposes. The number of octaves within the range of the instrument is determined by the size of the condenser and the primary number of oscillations. An apparatus of this kind permits staccato and glissando play. i

It is still another object of my invention to provide means for obtaining perfect legato play and to this end I provide two identical rotating plate condensers with levers and indicators which are alternately cut in and out, and both leverswith their indicators may move over .a single scale.

It is still another object of my invention to facilitate the playing of fast running passages, and to this end I provide contacts at the scale which are operated by the lever of the condenser or condensers so as to control the respective circuits.

It is still another object of my invention to provide means for generating octaves without the necessity of adding an octave in- Fig. 2 is an end elevation showing the lever terval for a given fundamental tone, as required in organs, pianos, etc.

The frequency or pitch is calculated by the Thompson formula:

in which L is the self-induction of the coil and C is the capacity of the condenser or condensers.

If the several intervals are generated by tuning with condensers the inductivity of the coil is constant.

.For fourfold inductivity the frequency is reduced for one-half, and, conversely, it is doubled for L, and this applies to all condenser values of the keyboard.

This is the principle of my octave switching which is not limited to an octave above and below, but, as shown by the formula, if L is increased nine or sixteen times or to one ninth or one sixteenth, it is possible to vary the pitch of the sound per octaves, increasing or reducing it,

In order to reduce this to practice in a musical instrument, it is necessary either to provide various tappings forthe coil in order to obtain the desired inductivity or to provide an arrangement of groups of coils which are adapted to be cut in or out as required, or to vary the inductivity of a coil by means of an iron core.

Any suitable means may be provided for cutting in and out the several coils or groups of coils, for instance, keys, push buttons, pedals or other mechanical means, and pneumatic or other means which, if desired, may be operated by a device inserted in the mouth of the operator.

If a fixed condenser is provided in the oscillation circuit and the coil is variable, that is, provided with tappings for the several sounds, or if a movable iron core effects the variations of the inductivity, the Thompson formula may be written as follows:

1 i N K K being a constant.

In the drawings aflixed to this specification and forming part thereof, means for controlling the-circuits connected with the scale, an instrument and a diagram of connections are illustrated diagrammatically by waiy of example.

' n the drawings,

Fig. 1 is a' perspective illustration showing a portion of a scale and a condenser lever,

and the stationary contact sectors with strip,

Fig. 4 is a detail illustration of Fig. 3 drawn to a larger scale,

-Fig. 5 is a perspective illustration of a musical instrument according to my invention,

Fig. 6 is a diagram of connections for this instrument, and

Fig. 7 is a diagram showing two variable frequency characteristics in an oscillating circuit.

Referring now to Figs. 1 and 2, l is a section of a scale, 2 is the operating lever which is moving above the scale and may be provided with an indicator, not shown; 3 are insulated contact sectors at the rear of the scale 1 4 is a movable contact secured to the lever 2 and adapted to cooperate with the contact sectors 3, and 5 is a push button on the lever 2 for closing the oscillation circuits (not shown). Means such as relays, (not shown), may be provided for controlling the circuits, the pitch of the sectors 3, 3 corresponds to the desired intervals. Any number of rows of sectors may be provided for playing fast running passages with various intervals.

As shown in Figs. 3 and 4, a corrugated contact strip is provided instead of the flat sectors 3, 3, and a contact 7 on the lever 2 cooperates with the strip 6, the circuit being opened when the contact is between two corrugations, and closed when the contact engages one of the corrugations as shown in play legato, as mentioned above. Indicators i 11 and 12 may be provided on the cranks.

Referring'now to Fig. 6, T is an electron tube, L-is an oscillating coil, C and C are two rotatingfiat condensers which are operated by the levers 2 and 9 illustrated in Fig. 5, R and R are two polarized relays, and T and T are contacts corresponding to the contacts 5, 11 by which the circuits of the condensers are closed.

Referring now to Fig. 7, L is a variable self-induction, and K is a variable capacity, for instance a condenser. vThe capacity or condenser K is adjustable through the medium of a handle 11 in combination with a scale 1 as shown in Fig. 5. The self-induction L is provided with means such as a movable contact 0 for regulating it. The capac-' tones within an octave and the self-induction L serves for regulating the octaves or the functions of the two characteristics K, L may be reversed. For instance the selfinduction L is regulated step by step from the value C to 4 C, 9 C etc., while the capacity K is either steadily reduced from L to L or the value L may be reduced in smaller steps down to L. 1 L. /5, etc. down to L. /1.

plunger condensers or carriage condensers,

may be provided or the rotary movement of the lever or levers may be changed into straight-line movement. In order to vary the timbre of the music the working points of the valve characteristics of the audion or the following tube are varied by varying the initial grid voltage.

The instrument may also be used for an imitation of elementary sounds, the condenser, the leak resistance and initial voltages of the grid in the audion being suitably selected. If the condenser and the grid leak resistance are considerable, the sound will be interrupted at the selected pitch by the charges and discharges of the grid within a given period. In this manner, birdsong, the splashing of water, wind and other sounds are excellently rendered.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof. I claim 1. An electro-acoustic musical instrument comprising electrical means for. generating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, said generating means compris-.

ing appliances for superimposing upon each other two ultra-audible oscillations and means for varying both oscillations by steps.

2. An electro-acoustic musical instrument comprising electrical means for generating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, said generating means comprising two oscillating high frequency circuits means for superposing the oscillations 0 said circuits so as to obtain audible frequencies, means connected with one of said circuits for varyingthe pitch of the beat-note and means for adjusting the other circuit so as to re-establish the same position within the scale throughout the range of said instrument.

3. An electro-acoustic musical instrument comprlsing electrical means for generating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, a lever adapted to make oscillation circuits and contact members operatively connected with said lever.

4. An electro-acoustic musical instrument comprising electrical means for generating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, a lever adapted to make oscillation circuits, a contact on said lever and stationary contact members adapted to be connected with said contact by means carried on said lever. I

5. An electro-acoustic musical instrument comprising electrical means for enerating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, a lever adapted to make oscillation circuits, a contact on said lever, and stationary contact members comprising eleva tions and depressions adapted to be connected with said contact on said lever by means carried on said lever.

6. An electro-acoustic musical instrument comprising electrical means for generating oscillations of audible frequency and means for translating the oscillations into perceptible sounds, a lever adapted to make oscillation circuits, a contact on said lever, stationary contact members adapted to be connected with said contact by means carried on said lever, and means for adjusting said stationar contact members.

An elec'Lro-acoustic musical instrument comprising an oscillation circuit, a condenser in said circuit, a lever for adjusting said condenser, a switch on said lever for cutting said condenser in and out, a second oscillation circuit, a condenser in said second circuit, a lever for adjusting said second condenser, a switch on said second lever adapted to cut in and out said second condenser, said switches being related in such manner as to prevent cutting in of both condensers at a time, and a tube to which said two oscillation circuits are connected.

8. An electro-acoustic musical instrument comprising an oscillation circuit, a variable self-induction and a variable capacity as frequency characteristics in said circuit, and means for varying one of said characteristics by a square law and for varying steadily the other characteristic;

9. An electro-acoustic musical instrument comprising an oscillation circuit, a variable self-induction and a variable capacity as frequency characteristics in said circuit, and

. means for varying one of said characteristics by a square law and for varying said other characteristic step by step at the rate of In teetimony whereof I afiix my signature.

JORG- MAGER. 

